Seidl will join McLaren "during 2019", the team announced on Thursday.
Seidl will report directly to Zak Brown, McLaren's chief executive, and has been charged with "responsibility for all aspects of the team's F1 racing programme". "To have an opportunity to contribute to the McLaren legacy is extremely special and inspiring".
It is unclear, however, if Seidl will be in place for the season-opener in Melbourne on March 17, as McLaren have not reached an agreement with Porsche on his start date.
"McLaren has the vision, leadership and experience but, most importantly, the people to return to the front, and that will be my absolute focus and mission".
"We are delighted that Andreas is joining McLaren to lead our F1 technical and operational program", Brown said.
Seidl is the fourth new management appointment since July, with three top-level figures having left as a outcome of McLaren's poor performance last season. "This is a significant appointment for us on two fronts", said Brown.
Seidl will be managing director of the F1 team, which McLaren says is the "latest step in the performance recovery plan and restructure". McLaren is also yet to confirm the start date of new technical chief James Key, who was signed from Toro Rosso previous year - Red Bull was reluctant to release him from his contract early.
Key will start work for McLaren this year, probably in the spring or early summer, once he has finished his "gardening leave" from former employers Toro Rosso.
Fernando Alonso, who scored 50 of McLaren's 62 points in 2018 has retired from F1, leaving British teenager Lando Norris and Spaniard Carlos Sainz to form a new-look partnership this year. Will they be let off the leash away from the track, or be "robotic" and heavily PR-ed like the old McLaren regime used to do with its drivers?
De Ferran's role will expand to take in the IndyCar programme and, potentially in the future, a world sportscar entry.
Former engineering head Pat Fry has returned to McLaren, who have also appointed Brazilian former Indy 500 victor Gil de Ferran as sporting director.